【摘 要】
：
Several studies have been performed in order to investigate the morphological and dynamic parameters of adroplet during the impact onto a rigid wall.Most of them involve single droplets,but very few a
【机 构】
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LEMTA-CNRS,University of Lorraine,France
【出 处】
：
13th International Conference on Liquid Atomization and Spra
论文部分内容阅读
Several studies have been performed in order to investigate the morphological and dynamic parameters of adroplet during the impact onto a rigid wall.Most of them involve single droplets,but very few are devoted to sprays with implementation of several diagnostics.Moreover,when sprays are involved,the liquid mass flux remains low(on the order of several kg/m2/s)and the case of a cold surface is mainly considered.Therefore,this experimental work aims at investigating the impingement of sprays onto a hot surfaces(up to 800℃)with liquid mass flux up to 13 kg/m2/s.Specifically,the main objective is to characterize the secondary droplets as a function of the surface temperature.To that purpose,a 2D Phase Doppler Analyzer(PDA)is synchronized to an infrared camera in order to measure simultaneously the droplets size and velocities simulatneously with the surface temperature and their time evolutions.Six full cone sprays are used in order to obtain a wide range of impingement conditions(normal incident Weber and liquid mass flux).A comparison of the impingement characteristics is also performed when the surface remains at room temperature.Additionally,the effect of the presence of the surface on the spray structure is also investigated.Results show clearly that incident droplet trajectories are modified by the presence of the solid wall itself and depend strongly on the temperature surface.The study of the impingement is mainly focused on the description of the mean diameter and the liquid mass flux after the impact.Main results show that the mean diameter of the secondary droplets remains constant in time during the Leidenfrost regime and increases for lower surface temperature.This behavior is strongly correlated to the liquid film formation for temperatures lower than the Leidenfrost point.The case of the expelled liquid mass flux after the spray has impinged the wall exhibits a similar behavior but it decreases after reaching the critical heat flux.It is attributed to the liquid film that becomes too deep,leading to a reduction of the number of expelled droplets.
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